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Cisco Bug: CSCus98541 - Switch changes locally administered bit to 1 when IPv6 multicast is sent

Last Modified

Jan 31, 2017

Products (1)

  • Cisco Catalyst 3850 Series Switches

Known Affected Releases

3.7(0)E

Description (partial)

Symptom:
Switch changes locally administered bit to 1 in MAC when IPv6 multicast packets with Link-Local scope (FF02::) are sent out via management interface (Gig0/0) for example MAC 20bb.c05e.f780 is changed to 22bb.c05e.f780. Other regular traffic is sent with correct MAC. 

This can cause problems that other end learns wrong MAC. If there is for example port security enabled this will cause security violation and port will go to err-disable state.

Conditions:
This is observed for all IPv6 multicast packets with Link-Local scope (FF02::) sent out via management interface (Gig0/0)

Problem with wrong MAC learing is observed when interface to which Gig0/0 is connected has portfast configured or when vlan that is assigned to this port has STP disabled - when interface is immediately ready to accept traffic.
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